In one process for the partial combustion or gasification of coal being developed, the coal is reacted at elevated temperatures and elevated pressures with a limited volume of oxygen. The reaction may be carried out in the presence of additional agents such as steam, carbon dioxide, or various other materials. The gasification of coal produces a gas, commonly known as synthesis gas, that contains mostly carbon monoxide and hydrogen. By a combination of factors, such as use of fine particulate dry coal, specially adapted and positioned "burners," e.g., such as described in U.S. patent application 156,675 (Hasenack et al) and U.S. patent application 156,679 (Hasenack et al), both filed Feb. 17, 1988 and incorporated herein by reference, as well as high temperatures and pressures not common in the art, conversion levels of coal are obtainable not previously reported. For example, conversion levels of greater than 98 percent, even 99 percent, basis carbon, may be obtained. Also produced are varying quantities of other gases, such as carbon dioxide and methane, and various liquid and solid materials, such as small particles of ash and carbon commonly known and collectively defined herein as flyslag or flyash. This flyslag, it has been determined, because of the high rate of conversion, does not have the lubricity associated with lower conversion rates, and tends to be different in composition and properties from flyash normally associated with combustion boilers and other processes. In general, the flyslag or flyash entrained with the gas, after solidification, is usually removed from the raw synthesis gas by a combination of cyclones or separators, or a water scrubbing system employing washer coolers, venturi scrubbers, or filters or electrostatic precipitators, or combinations of these systems.
As the flyslag leaves the gasification reactor or zone, it is molten and precaution must be taken to prevent deposition of the sticky particles on the walls of the subsequent stages in the form of strongly adhering layers. For example, a number of patents describe a variety of quenching techniques, such as the use of a cool recycle gas designed to solidify the particles and prevent adhesion, and some patents describe the use of rappers to easily dislodge weakly adhering layers. The invention also addresses this problem.